1. The Field of the Invention
The present invention relates to a method and structure for packaging an integrated circuit, and more particularly to a method and structure for packaging an integrated circuit with a readily removed excess encapsulant on a degating region, in which the excess encapsulant left on a mold runner can be readily removed to solve problems of insufficiency in wiring space, reducing a line density in circuitry and increasing manufacturing costs due to reserving a degating region on a substrate in advance for a purpose of peeling away the excess encapsulant from the degating region without damaging the substrate.
2. Description of the Related Art
When a ball grid array (BGA) packaging substrate is generally designed, an area corresponding to a position of a mold runner must be reserved for smoothly performing an encapsulation operation and an encapsulant material left on this area has to be easily peeled away from this area without damaging the substrate. For this, as in an application of U.S. Pat. No. 5,635,671, titled "MOLD RUNNER REMOVAL FROM A SUBSTRATE-BASED PACKAGED ELECTRONIC DEVICE", a degating region is primarily defined at a corresponding area on the substrate and the excess encapsulant left on the degating region can be easily peeled off without damaging the substrate since an adhesive force between the metal on the surface of the degating region and the encapsulant material is much smaller than the adhesive force between the metal and the substrate. The application to a BGA packaging substrate is described as follows. As shown in FIG. 5, a chip attachment area 52 is formed at a center portion of the substrate 50, a wiring area 51 formed by a very complicated wiring pattern surrounds the chip attachment area 52, an encapsulated package area 54 is covered with the encapsulant material and a cutting line 55 is prepared for cutting the substrate of a bar shape into a plurality of single unit packages. In addition, a degating region 53 formed at one corner of the substrate 50 beyond the cutting line 55 corresponding to a mold runner for receiving the encapsulant material is used for readily removed the encapsulant from the degating region 53 without damaging the substrate 50. Although the problem that the encapsulant can be easily peeled away from the degating region is solved by the above design, other shortcomings will be generated in a practical application which are as follows.
1. Because the degating region occupies a portion of a surface area of the substrate, not only is a difficulty in designing the wiring pattern increased, but also a reduction in a production yield and an increase in a noise interference are generated due to over-condensed regional circuit lines. PA1 2. Because the degating region is reserved on the substrate, a manufacturing cost is raised since a metal area on the entire substrate surface is increased, which causes a quantity of material used in a subsequent gold-plating operation to be increased. PA1 3. The degating region formed on the substrate continuously varies with the design of a mold tool, which results in defects of low cost-effectiveness and wasting of designing costs since the design of the substrate has to be changed regularly.
The present invention provides a better solution to overcome the problems existing in the prior art.